This section is intended to provide a background or context to the invention recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Refrigeration systems typically include a refrigerant that circulates through a series of components in a closed system to maintain a cold region (e.g., a region with a temperature below the temperature of the surroundings). One exemplary refrigeration system includes a direct-expansion vapor-compression refrigeration system including a compressor. Such a refrigeration system may be used, for example, to maintain a desired low temperature within a low temperature controlled storage device, such as a refrigerated display case, coolers, freezers, etc. in a low temperature subsystem of the refrigeration system. Another exemplary refrigeration system includes a chilled liquid coolant circulated by a pump to maintain a desired medium temperature within a medium temperature storage device in a medium temperature subsystem of the refrigeration system. The low and/or medium temperature subsystems may each receive cooling from one or more chiller units in a cascade arrangement. The chiller units circulate a refrigerant through a closed-loop refrigeration cycle that includes an evaporator which provides cooling to the low temperature subsystem (e.g. as a condenser) and/or the medium temperature subsystem (e.g. as a chiller).
Accordingly, it would be desirable to provide a cascade refrigeration system having one or more modular chiller units capable of using ammonia as a refrigerant for providing condenser cooling in a low temperature subsystem of the refrigeration system, and/or for chilling a liquid coolant for circulation through a medium temperature subsystem of the refrigeration system.